Field of the Invention
The present invention is directed to methods of producing fluorosulfonate esters, related salts, and related compositions comprising fluorosulfonate esters.
Background
Organic salts of fluorosulfonate (FSO3−) are useful, for example, as ion transport agents, in the fields of organic compound syntheses, as electrolytes and the like.
In 1968, the alkylation of triethylamine with ethyl fluorosulfonate in acetonitrile, to give tetraethylammonium fluorosulfonate, was reported (see Ahmed, M. G.; Alder, R. W.; James, G. H.; Sinnott, M. L.; Whiting, M. C., Chemical Communications (London) 1968, 1533-1534). The salt was not isolated, and no alcohol was present in the reaction.
In 2010, a quaternary ammonium fluorosulfonate was described by Ishii and coworkers (EP2243769, US20100087673) as a byproduct of the reaction of sulfuryl fluoride (SO2F2) with a hindered primary alcohol in the presence of triethylamine, giving the byproduct in 33% yield.
In 2012, a large number of organic fluorosulfonates were described in two patent applications (EP2535976 and US20120308881). Actual procedures for the preparation of organic fluorosulfonates were not reported, only possible methods. In particular, these applications included a general description of “a method in which a fluorosulfonic acid ester is reacted with a tertiary amine, a phosphine, or the like to obtain the fluorosulfonic acid salt through the quaternizing reaction of the tertiary amine or phosphine.” Neither a description of methods of manufacture of the fluorosulfonate ester precursors, nor of the reaction of these esters with the amine, was given.
Some fluorosulfonate esters are highly toxic, especially the lower alkyl esters MeOSO2F and EtOSO2F, making it impractical to handle these compounds on a commercially viable scale. It is preferable to generate a fluorosulfonate ester in the same pot as a substrate in order to minimize contact with and exposure to the fluorosulfonate ester.
Generation and reaction of fluorosulfonate esters in a single pot have been tried. However, a deoxyfluorination reaction, wherein an alcohol is converted to an alkyl fluoride, is generally reported. Organic fluorosulfonate salts, if present, are undesired byproducts obtained in low yield (see e.g., U.S. Pat. No. 7,807,858, U.S. Pat. No. 8,058,412, U.S. Pat. No. 8,217,196, U.S. Pat. No. 8,283,489, U.S. Pat. No. 8,304,576, US20080125589, US20090250658, US20100087673, US20110201825, EP2243769).
Perfluoroalkanesulfonate onium salts (RfSO3−M+), have been made from perfluoroalkanesulfonyl fluorides (RfSO2F), silyl ethers, and aprotic amines, in a single pot (see Beyl, V.; Niederprüm, H.; Voss, P., Justus Liebigs Annalen der Chemie, 1970, 731, 58-66); however, SO2F2 is not mentioned.